Catamarans and trimarans, being normally unballasted, float with great
stability either way up. A float at the masthead should prevent the im­mersion
of the mast, and thus ensure that the craft never gets into the stable, in­verted
attitude. Some floats are made of lightweight foamed plastic, or are
air-fIlled hollow chambers. Others are bladder-like, to be inflated
automatically from a carbon dioxide cylinder if the boat goes beyond a certain
angle of heel.